PULSE OXIMETER

Solomon C. Nwaneri, PhD, Department of Biomedical Engineering, University of Lagos. E-mail: snwaneri@unilag.edu.ng


A pulse oximeter is a medical device used to measure oxygen saturation (SpO2) in the blood. It is a non-invasive device. This means that the device does not penetrate or break into the skin. The blood needs a minimum amount of oxygen for the body to survive which is usually 95%. If the oxygen saturation is lower than the prescribed limits, a person is exposed to a condition referred to as hypoxemia. 

Hypoxemia refers to oxygen levels that are lower than the normal saturation. This condition is characterized by shortness of breath and sometimes headache. Hypoxemia is usually caused by underlying diseases such as sleep apnea, lung diseases and several other possible causes. Oxygen should be in the haemoglobin of the blood known as oxyhaemoglobin(HbO2).

Pulse oximeters operate based  on the absorption of different wavelengths of light. Usually, Red and infrared light are the two colors of light involved. These both absorb  oxygenated and deoxygenated in different ways. 

Oxygen concentration, SpO2 is calculated as:

SpO2 = Oxyhaemoglobin/(Oxyhaemoglobin + Deoxyhaemoglobin)



Fig. 1: Pulse Oximeter

Apart from the conventional pulse oximeters, there are veterinary pulse oximeters designed specifically for for animals. They are similar in operation to the conventional pulse oximeters as they usually measure pulse rate and oxygen saturation. This is particularly important in veterinary practice and  animal studies.


  Fig. 2: Veterinary Pulse Oximeters




Keywords: Hypoxemia, Oxyhaemoglobin, Oxygen Saturation, Pulse Oximeters, and Veterinary Pulse Oximeters



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